Radio-Frequency Identification (RFID) systems typically include RFID tags and RFID readers. RFID readers are also known as RFID reader/writers or RFID interrogators. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are particularly useful in product-related and service-related industries for tracking objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package.
In principle, RFID techniques entail using an RFID reader to interrogate one or more RFID tags. The reader transmitting a Radio Frequency (RF) wave performs the interrogation. The RF wave is typically electromagnetic, at least in the far field. The RF wave can also be predominantly electric or magnetic in the near field.
A tag that senses the interrogating RF wave responds by transmitting back another RF wave. The tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. Backscatter may take place in a number of ways.
The reflected-back RF wave may further encode data stored internally in the tag, such as a number. The response is demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data can denote a serial number, a price, a date, a time, a destination, an encrypted message, an electronic signature, other attribute(s), any combination of attributes, and so on.
An RFID tag typically includes an antenna subsystem and a radio subsystem including a modem, a power management section, a logical section, and a memory. In some RFID tags the logical section may include a cryptographic algorithm which, in many instances, relies on one or more passwords or keys stored in tag memory. In some RFID tags the power management section may include an energy storage device such as a battery. RFID tags with an energy storage device are known as active or battery-assisted tags. Advances in semiconductor technology have miniaturized the electronics so much that an RFID tag can be powered solely by the RF signal it receives. Such RFID tags do not include an energy storage device such as a battery, and are called passive tags. Regardless of the type, all tags typically store or buffer some energy temporarily in passive storage devices such as capacitors.
Counterfeiting is a problem in many areas of global commerce. For example, retail-goods manufacturers, such as manufacturers of luxury clothing or purses, often find counterfeit items in the marketplace. Many commercial enterprises envision using cryptographically secure RFID systems to ascertain whether a tagged item, or more particularly the tag attached to an item, is genuine and not counterfeit. However, these commercial applications are loathe to adopt anticounterfeiting systems that require password or key distribution, because securely managing and distributing passwords or keys among global trading partners is difficult.